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November 15-16 Snowfall Potential


Hoosier
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DTX - Oh the dreaded and ever-present sensitivity to track concerns around here - sigh

High pressure is on schedule to build across the Great Lakes by
Monday to start the week with dry weather. The high holds into
Tuesday as the next low pressure system gathers organization over
the Plains and Midwest. This large and intense system sweeps Gulf
moisture northward which could reach Lower Mi as early as Tuesday
afternoon in the form of a rain/snow mix. A heavier mix of rain and
snow changing to all snow becomes possible Tuesday night into
Wednesday as extended range models show the surface low center
tracking nearby across NW Ohio, a track that makes the forecast for
SE MI very sensitive to the small adjustments likely in upcoming
forecast cycles.

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11 minutes ago, A-L-E-K said:

Would be lightly hyped if cold, but since warm and winds off lake going dab

Nice to see euro still the premier fantasy snow model

Probably a decent call for your backyard.

Assuming lake temps are still near 50 by Tuesday morning (nearshore temps are currently ~53), that is often going to be a problem when winds are onshore and 850 mb temps "only" around -7C to -8C.  The low level flow does not look that strong, so the marine influence shouldn't extend too far inland (ORD/MDW should largely be safe from it imo), but lakeside will be battling.

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Sort of tricky to figure out where the highest amounts will be in LOT's area.  There is a lake signal showing up (trending more favorable toward nw IN with time) but that will be countered by warmer low level temps near the lake.  If I had to bet I'd go with somewhere a little inland in northwest IN by the time it's all done but not the greatest confidence.

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Granted it's the NAM at 84 hours, but just showing it to make a general point as ultimate location may be different.  We can use the 850 mb vertical velocity output as a proxy for the lake effect band location, and as you can see, there's a strong signal in and around Porter county Indiana on the NAM at that time.

850hvv-us-mw.png

Pulling a forecast sounding from northern Porter county reveals a deep layer of relatively steep lapse rates and good moisture in the low-mid levels, so we're working with very good inversion heights and implied lake-induced EL heights if modifying for lake water temps.  Getting precip won't be a problem.  The bigger question is how far inland will you have to go to get away from the marine warmth, thus having some better accumulation potential.

nam-2022111318-084-41-54-87-1.png

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14 minutes ago, Chicago Storm said:


Easy toss.

There was hope that the elevation correction earlier this year would fix the overzealous LE output, but clearly it didn’t.


.

That being said, I'd be pretty surprised if the highest amounts in the area aren't somewhere in a zone inland from Lake Michigan.

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Tough call here.  There's a scenario where if the lake cooperates that I could envision about 3-4", but that's probably near best case.  More likely to be less than that, but whatever falls probably won't actually be what's on the ground because of melting in between.

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LOT AFD for @Hoosier...

"IN FACT, LAKE TEMPERATURES OF +10   TO +11C AND 850MB TEMPERATURES OF -6 TO -7C AS WELL AS INVERSION   HEIGHTS PUSHING 11,000-12,000 FEET WILL GENERATE AS MUCH AS 250-350   J/KG OF LAKE-INDUCED CAPE FROM LATE TUESDAY AFTERNOON THROUGH EARLY   WEDNESDAY MORNING, LEADING TO CONCERN THAT LAKE ENHANCEMENT TO SNOW   MAY "OVERACHIEVE" IN SPITE OF MARGINAL SURFACE TEMPERATURES.   INTERESTINGLY, THE 12Z HREF SHOWS SPLOTCHY 20-30% PROBABILITIES OF   SNOW RATES >1"/HR BETWEEN 2-3 PM TUESDAY AND 3-4 AM WEDNESDAY ACROSS   THE NORTHERN CHICAGO SUBURBS. PERHAPS MORE CONCERNING IS THE 12Z   HREF 24-HOUR LOCAL PROBABILITY-MATCHED MEAN QPF OF 0.75-1.00" ACROSS   LAKE, COOK, AND NORTHEASTERN DUPAGE COUNTIES. WHEN APPLYING A   STANDARD 10:1 SNOW RATIO, IT'S EASY TO SEE HOW SNOW TOTALS MAY GET   OUT OF HAND. HOWEVER, WITHOUT A PERSISTENT BAND HITTING THE SAME   AREA FOR HOURS AND HOURS, IT MAY BE TOUGH TO TRULY REALIZE THE   SNOWFALL AMOUNTS ADVERTISED BY INDIVIDUAL HIGH RESOLUTION CAMS THAT   INFORM THE HREF. FOR NOW, WE WILL CAUTIOUSLY ADVERTISE AN ADDITIONAL   2-3 INCHES OF SNOW ON TOP OF WHAT FALLS IN THE MORNING KEEPING IN   MIND OUR FORECAST MAY BE WAY TOO LOW."

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18z HRRR 

HRRRNIL-prec-kuchsnow-048.png

 

I guess the question for the downtown Chicago area is whether there will be a window where the convergence axis starts to shift eastward and flip winds offshore while still having some precip around.  That is sort of being hinted at on Wednesday and may represent a little better opportunity for the core of the city, but overall the better place to be is inland.

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10 minutes ago, hardypalmguy said:

Never bank on warm lake temps keeping it all rain.  Remember in October 1989, MKE got over 6" of lake effect snow.  Same thing happened in November sometime in the 90s.

It's part science and part art when it comes to figuring out how much/how far inland for the marine influence.  Warm lake = rain can definitely be overly simplistic.  There are all kinds of factors that go into it, such as how cold the airmass is, lake water temps, exact wind direction, wind speed, precip rates.  If we had 850 mb temps of -15C tomorrow, then Alek would be ripping snow with significant accumulations lakeside despite onshore flow and water temps of 50+.  But we don't have that so it's a more nuanced picture as you move from lakeside to farther inland.

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